Known in the past has been an internal combustion engine performing premixed charge compression ignition (PCCI) in part of the operating regions of an internal combustion engine. Premixed charge compression ignition is a form of combustion where fuel and air are premixed, then the premixed gas is self-ignited. In premixed charge compression ignition, fuel and air are mixed in advance to a certain extent in this way, then the air-fuel mixture is burned, and therefore there are few locations with locally high concentrations of fuel when burning the air-fuel mixture. As a result, the amount of discharge of smoke can be suppressed.
Further, in performing premixed charge compression ignition, it is known to inject fuel from the fuel injector by main injection and pre-injection before main injection (for example, PLT 1). In particular, in PLT 1, the injection timing of the main injection is fixed and the injection timing of the pre-injection is changed according to the engine operation state, etc., or the injection timing of the main injection and the injection timing of the pre-injection are both changed in the same extent, according to the engine operation state, etc.